Buffered Store Filter

Buffered Store Filter

Hi,
I want to implement a Store.filter() on a buffered store.
The store has the following config :
buffered: true,
remoteSort: true,
pageSize: 200
which enables it to be a buffered store.

The problem is , since pageSize is 200, and grid is loaded with first available 200 records.
However, there are a total of ,say, 500 records in database, which populates in subsequent scrolling of verticalScroller : 'paginggridscroller'.

Now, on first grid load, user should be able to filter/search on the entire 500 set of records, and not only in the loaded 200 records, before he scrolls, to see the remaining 300 records in UI.

How to achieve this - Grid loaded with first 200 reords, but, search/filter in the entire 500 records to be available, before user scrolls for the first time.